Hollow artificial silk of low luster and process of preparing the same



Patented Sept. 6, 1932 UNITED STATES PAT NT DQFFIQIQE HENRI LOUIS, BARTHELEMY, ROME, GEORGIA HOLLOW An'rIrIoIALsrLK or Low nnstrnn Ann rnocnss or PREPARING THE SAME No Drawing.

a partially collapsed.

7 liquid that does not dissolve cellulose acetate Heretofore attempts have been made to produce hollow filaments of artificial silk,

for example, by first producing the-filaments with a solid or liquid substance, such as wax or oil in the filament, which is afterwards eliminated by washing out the solid or liquid substance, leaving the filaments hollow.-

Also, with cellulose acetate, a slow solidification of the spun filaments is caused to take place, fOilOVv l by a more rapid solidification for the purpose of making the filaments hollow. Others have attempted to make hollow filaments by introducing plasticizers, such as diacetone alcohol, into the spinning liquor and removing the plasticizingagent by'extraction with water or other solvent after the filament has been spun. The use of toluene and water together, has also been tried for this purpose. These attempts have not been entirely successful and, in addition, the filament produced possessed highluster that is objectionable to most users.

A want has existed for a long time for low luster hollow filaments of cellulose acetate or cellulose nitrate that could be produced rapidly and economically and still have high tensile strength. The hollow filaments make a cloth or fabric that is warm, due to the enclosed air which gives the same better heat insulating qualities; the filaments are lighter than solid filaments and, therefore, a pound of hollow filaments will make more cloth than the same weight of solid filaments; and the fabric made of the hollow low luster filaments will correspond more nearly to wool, although it has the appearance of silk. 7

In carrying out this invention, an organic or cellulose nitrate is mixed with a solution of cellulose acetate or cellulose nitrate which is used for spinning the filaments, this liquid being such that it will evaporate rapidly when a hot current of air comes into contact with the filaments just after they are ments;

Application filed September 15, 1930. Serial No. 482,161.

.siderably to elongate them, thestretching in some instances being sufficient to double the length of the filaments, withoutmaterially decreasing the tensile strength of the fila- The stretched filaments of smaller cross-section than the ordinary filaments have in some instances been. found to be. practically as strong as the unstretched filaments. I p f I f I do not wish to restrict myself to any par ticular. explanationof why the addition of.

the non-solvent to thesolution causes the filaments to behollow and of low luster when they are spun, but from observations that I have made, it seems that either the liquid thatis BOT- mixed with the solution formsa constant boiling mixture of low boiling temperature which is driven ofi early in the process of drying, thereby causing a hardening of the surfaces of the filaments after which the low boiling mixture'is evaporated from the interior, leaving the filaments hollow, or the solvent for the cellulose acetate or cellulose nitrate evaporates out of the mixture at the surface of the filament, causing a hardening of the surface orprecipitation of the cellulose compound in the form of a tube which, upon further drying, has its interiorcontents precipitated within the tube, producing'a hollow structure. 'The walls of the tube collapse, so that the filaments are not round and do not possess high luster.

' The following is given as a specific example of carrying out the invention, but it is to be understood that the invention is not restricted to the particulars mentionedin the example: Gelluloseacetate (containing about 4% ofm'oi'sture) is dissolved in an anhydrous mixture of about of acetone and 10 of isopropyl ether. The solution is spun by an I ordinary spinneret into a cell through which,

hot air is circulating at a temperature between about F. and F. and is capable of containing about 100 to 350 grams winding the same at the proper speed upon a reel While it is passing through the heated cell. The tensile strength of the filaments both dry and wet and their elongation both i dry and wet are substantially the same as filaments made from ordinary artificial silk solutions using acetone alone as a solvent.

The amount of the isopropyl ether mentioned in the above example may be varied from about-5% to 20% instead of 10% without essential changes in the properties of the filaments. nets of isopropyl ether such as monochlor isopropyl ether and dichlor isopropyl ether, may also be used.

This invention is applicable to spinning solutions which do not contain substances that react with isopropyl ether, and primarily to those which are spun dry. In general it ap plies to spinning solutions containing cellulose esters and /or ethers.

I claim:

1. The process of making hollow filaments of artificial silk which comprises spinning asolution of a cellulosic compound selected from the ester and ether groups, and containing an other selected from the group consisting of isopropyl ether and its halogenated derivatives.

2. The process of making hollow filaments of artificial silk which comprises spinning a. solution oi a cellulosic compound selected from the ester and ether groups, said solution containing isopropyl ether.

3. The process of making hollow filaments of artificial silk which comprises spinning a solution oi a cellulosic compound selected from the ester and ether groups, said solution contaning halogenated isopropyl ether.

i. The process of making hollow filaments oii artificial silk as set forth in claim 1 in which the solution is spun into a drying Zone having an atmosphere capable of containing 100 to 350 grams of vapor per cubic meter.

5. The process of making hollow filaments of artificial silk as set forth in claim 1 in which the solution is spun into a drying Zone having an atmosphere capable 01 containing 200 to 300 grams of vapor per cubic meter.

6. The process of making hollow filaments of artificial silk which comprises spinning an acetone solution of a cellulosic compound selected from the ester and other groups, said solution containing isopropyl ether.

7. The process of making hollow filaments oi artificial silk which comprises spinning an acetone solution of a cellulosic compound selected from the ester and ether groups, said solution containing isopropyl ether in an amount approximating ten per cent of the amount of acetone.

8. The process oi making hollow filaments of artificial silk which comprises spinning a solution of cellulosic acetate containing an ether selected from the group consisting of l-l'alogenated substitution prod-,

isopropyl ether and its halogen derivatives;

9. The process of making hollow filaments of artificial silk which comprises spinning a solution of cellulose acetate containing isopropyl ether.

10. The process of making hollow filaments of artificial-silk-which comprises spinning an acetate solution of cellulose acetate containin g isopropyl ether in an amount between 5 and 20per cent of the amount of acetone.

11. The process of making hollow filaments of artificial silk which comprises spinning a solution of nitrocellulose containing an other selected from the group consisting of isopropyl ether and its halogenated derivatives.

12. The process of making hollow filaments of artificial silk which comprises spinninga solution of nitrocellulose containing isopropyl ether. I

HENRI L. BARTHELEMY. 

